Even though differentiated light is the "formal object" of eyesight, we do not experience it directly. Rather, light tends to serve as an invisible representative of the world to us. We learn of its nature by its interaction with other things.
Since cameras are sensitive to light, but possess many functional differences from our eyes, this has made photography an inevitable venue for exploring – and being surprised by – light. In the case of this collection, it plays with the peculiar interaction between a circular polar lens filter and the polarising coating on train windows.
When diverse polar filters are overlaid, they can produce patterns of constructive and destructive interference. Instead of permitting light of only a certain polarity to reach the sensor, light of a given polarity (say, linearly polarised in the vertical direction) is first admitted through a medium, after which it is filtered in a different way (for example, by a circular polar filter). This results in some areas of a photograph being double-polarised, which end up looking dark, while other areas remain unfiltered by either filter.